Cross-bar switch



Sept. 20, 1955 K. A LUNDKVIST ET AL CROSS-BAR SWITCH 4 Sheets-Sheet 1 Filed Oct. 15, 1951 Sept. 20, 1955 K. A. LUNDKVIST ET AL 2,718,559

CROSS-BAR SWITCH Filed Oct. 15, 1951 4 Sheets-Sheet 2 lzbv azzrtol Sept. 20, 1955 K. A. LUNDYKVIST ET AL 2,718,559

CROSS-BAR SWITCH Filed 001;. 15, 1951 4 Sheets-Sheet s lzz/v arzrbom K .11 .L canal/570L623 Sept. 20, 1955 K. A. LUNDKVIST ET AL 2,718,559

CROSS-BAR swzwcn Filed Oct. 15, 1951 4 Sheets-Sheet 4 H 10 E i J lrvv GZZ'ZZOIWS .Kfl,L Mil! LS'ZJ United States Patent CROSS-BAR SWITCH Karl Axel Lundkvist and Eric Axel Wiberg, Stockholm, Sweden, assignors to Telefonaktiebolaget L M Ericsson, Stockholm, Sweden, a company of Sweden Application October 15, 1951, Serial No. 251,272 Claims priority, application Sweden October 23, 1950 8 Claims. (Cl. 179-2754) The present invention relates to an automatic selecting device for telephone exchanges. The selecting device is of the cross-bar switch type with sets of contact strips crossing each other or other conductors arranged in two parallel planes, a front one and a back one, within a frame. For each one of the sets of contact strips in the front plane there is a selecting bar and an electromagnet actuating said selecting bar so that the set is marked for connection with a set of contact strips or conductors in the back plane. For each one of the sets of contact strips in the back plane there is an operating bar and an electromagnet actuating said operating oar, whereby the contact strips of the set are connected with each one of the contact strips in a set of contact strips in the front plane marked by a selecting bar.

A number of different constructions are known to produce a contact between the above mentioned sets of contact strips crossing each other, but they have not been used practically partly because the mechanical devices were too complicated and partly because the contact points were inaccessible and unsatisfactory. Cross-bar switches with contact strips in the direction of the operating bars only and loose contact spring assemblies in the direction of the selecting bars have been used instead. They are rather expensive in part owing to the assembly work for the contact spring sets, in part owing to the connections in the direction of the selecting bars. These connections cannot be made of open wire but are made of insulated wire, which is peeled and soldered at each contact point. The present invention removes all said disadvantages and simultaneously good and easily accessible contact points and a simple mechanism is obtained, just as in a cross-bar switch with loose contact spring assemblies.

This is achieved by arranging detachable units on both sides of a frame, each detachable unit comprising a set of conductors and the conductors mounted on one side of said frame crossing the conductors mounted on the opposite side of the frame, and by arranging contact springs at each crossing point which are selected by the Selecting bar and operated by the operating bar of the crossing point, and which are fixed to the conductors in one of the detachable units and when operated make contact with the conductors in the other detachable unit in the crossing point.

A further advantage achieved by the invention is that the selecting bars are placed between two planes in which the contact strips lie, which entails, that the contact points lie in front of the selecting bars instead of behind them as in most other cross-bar switches, the contact points thereby being easily accessible for inspection and cleanmg.

Another advantage achieved by the invention is, that each selecting bar with its electromagnet can be combined with the contact strips corresponding to the selecting bar to form a detachable selecting unit, similarly to What has already been usual earlier with regard to the operating bars.

2,718,559 Patented Sept. 20, 1955 The invention will be described more closely below with reference to the accompanying drawings Figs. 1:12.

Fig. 1A is showing the principle for a cross-bar switch according to one embodiment of the invention.

Fig. 1B is showing a corner of the same cross-bar switch completed with some essential details.

Figs. 2-3 and Figs. 11-12 show details and different embodiments of the vertical detachable units in 'Figs. lA-B.

Fig. 4 is showing a cross-bar switch according to a second embodiment of the invention.

Figs. 510 show details and different embodiments of the vertical detachable units in Fig. 4.

A frame 1 is the body of the crossbar switch in Fig. 1A. On the front side of said frame vertical sets 8 of contact strips are fixed. Each vertical set comprises three contact strips insulated from each other and provided with soldering tails 20. A contact pin 9 extends from each one of said strips at each crossing point with an operating bar, for example 5b. To each vertical set there further pertains a support 14, against which the tongues 6 of the horizontal contact strips 3 rest when in their rest position. The support is made of insulating material. An angle 19 is at its top fastened to the support.

The vertical contact strips and the support are joined for example by means of screws or rivets, glued or cast with moulding material, and fastened at their bottom to the yoke of an electromagnet 10. A selecting bar con? sisting of a fiat strip .1 is fixed to or is a portion of the armature of the electromagnet 10 and is turnably mounted in the angle 19 and the yoke of the electromagnet.

On the back side of the frame 1 horizontal sets of con? tact strips 3 are fastened. Only one set comprising three contact strips is shown in the figure. The contact strips are joined by means of blocks 15, 16, 17 of insulating material and provided with tongues 6 at each crossing point with a selecting bar such as shown at 11. The contact strips 3 are provided with soldering tails 21. The yoke of an electromagnet 4 is fixed to the block 15. The operating bar 511 consists of a rigid strip, which is provided with a lever 2 for each crossing point between the operating bar and a selecting bar 11. There is for each lever an indicating device 7 consisting of a resilient wire fixed at one of its ends to the operating bar 512 and resting against the selecting bar 11. The free end of the wire is provided with a plate 13, which is for example painted white to be easily visible. The resilient tongues 6 pertaining to the same crossing point are connected to a driver 12 of insulating material.

The function of the cross-bar switch corresponds wholly to the function of a normal cross-bar switch with individual spring sets at each crossing point. A line connected to the soldering tails 20 is marked by the electromagnet 10 being energized, attracting its armature and revolving the selecting bar 11. The wire 7 is thereby conveyed below the driver 12 and above the lever 2. The line connected to the soldering tails 21 is selected by electromagnet 4 being energized, attracting its armature 5a and revolving the operating bar 5b. The wire 7 is thereby pressed between the lever 2 and the driver 12 and the tongues 6 are lifted and make contact with the contact pins 9. The selecting magnet 10 can then release its armature and the wire 7 remains pressed between lever and driver.

Should the electromagnet 4' actuate the operating bar 5 b without the electromagnet 16 actuating the selecting bar 11, the lever 2 will swing up behind the driver 12 without touching it. Simultaneously, the wire 7 is con veyed up beside the driver 12. Should then the selecting bar 11 be revolved by the electromagnet 10, the wire 7 will rest against the side of the driver 12 and be bent.

The plate 13 is normally hidden by the contact strips 8 and the supporting rib 14, but when it is conveyed below the driver 12 it becomes visible from the front and indicates, that the crossing point has been marked.

It should be pointed out, that the invention is not limited to whole contact strips as in the example described above. The vertical contact strips may thus be exchanged for soldering fields with rows of contact pins connected with vertical multiple connections, and the horizontal contact strips may be replaced by loose spring assemblies connected with horizontal connections of for example smooth wire. Other equivalent means may also be used without the idea of the invention being set aside. In the figure it is supposed that a selecting bar is used for each vertical set of conductors, but each selecting bar may naturally be common for two sets, as is usual with conventional cross-bar switches. The selecting bar is thereby actuated by two electromagnets, by which it is turned in one or the other direction from an intermediate position.

It is important that the two kinds of detachable units, which are mounted on opposite sides of a frame, have determined positions relatively each other, so that the contact springs, which have to make contact between the conductors in the different units, determine the contact distance in relation to the fixed contacts of the conductors. The conductors on one side must further be provided with contact pieces corresponding to said contact springs.

This is achieved in cross-bar switches according to the invention by arranging a first supporting bar to which the conductors pertaining to an operating bar are fixed, and by providing a lever protruding from each one of said supporting bars at each crossing point, a groove in the other one of said supporting bars corresponding to said lever, which is supported by said groove, said contact springs resting on said lever.

Fig. 1B shows a corner of a cross-bar switch where a vertical and a horizontal set of conductors cross each other in a frame 1. The vertical conductors 8 are fixed to a supporting bar 14 and provided with contact pieces 9, which will be more closely described below with reference to Figs. 23. The horizontal conductors 3 are located in grooves in a strip of insulating material, which in its turn is fastened to a supporting bar 22. From the supporting bar 22 a lever 22a protrudes at each crossing point for the horizontal conductors 3. The lever 22a rests in a groove 140 in the supporting bar for the vertical conductors 8 and supports the lifting bar 12 for the contact springs 6, which protrude from the conductors 3.

The lifting bar 12 further rests against a lifting spring 23a, the front part of which is bent down right outside the tip of the lever 2 on the operating bar 5b. An indicating device consisting of a resilient metal-wire 7 is fastened on the operating bar 5b and runs in parallel with the lever 2 between said lever and the supporting bar 14. The vertical supporting bar 14 with conductors 8 is pertaining to a selecting bar 11 and its electromagnet, both bars forming together a unit. The shape of the supporting bar appears from Fig. 2. On the front part of the bar the conductors 8 are located in vertical grooves. At each crossing point for a conductor 8 there is a window 14a and a contact piece 9 according to Fig. 3. The contact piece 9 is angular and one of its legs is on its upper side covered with a plate of insulating material 9a. The contact pieces 9 are passing through square holes in the supporting bar 14, each one being on the same level with one of the windows 14a. The conductors 8 are provided with a bending at each window 14a, so that they come into contact with the corresponding contact piece 9 and can be soldered to said piece. At 14b, the supporting bar is Warm-pressed so that the grooves are filled and the upper end of the conductors are steadily fixed.

The supporting bar 14 is further provided with a bracket 14d supporting the selecting bar 11, and a groove at each crossing point for guiding the lever 22a in Fig. 1B. The selecting bar 11 is threaded through a hole in the bracket 14a. The contact springs 6 in Fig. 1B are bent so that they stretch downwards and hang onto the lifting bar 12, which in its turn hangs onto the lever 22a. The lifting spring 23a is bent upwards so that it easily presses against the lifting bar 12. The position of the contact springs will thus at rest be deter mined by the lever 22a, which is rigid, but however allows small movement upwards or downwards, when it is pressed down into the groove 140 on the supporting bar 14. The contact pieces 9 have fixed positions with relation to the groove 14c, and therefore determined contact distances are obtained between the springs 6 and the contact pieces 9.

The selecting bar 11 is provided with a bending 11a at each crossing point, which actuates the indicating device 7 when the selecting bar is turned, so that said device is introduced between the lever 2 of the operating bar and the lifting spring 2312. When the operating bar 5b is turned by its magnet, the indicating device 7 is squeezed and the springs 6 lifted so, that they come into contact with the contact pieces 9.

Another embodiment is shown in Figs. 1l-l2. Here the vertical conductors 8 consist of bands with cuttings and bendings 9 on one edge. The bands are united at some distance from each other by means of strips of moulding material, in which there are grooves 14c for guiding the lever 22a in Fig. 1B. The vertical set of conductors 8 is in this case somewhat flexible, and therefore the lever 22 sets the contacts 9 sidewise when guided into the groove 140. In Fig. 1A the contact springs are fastened to the horizontal conductors as in Fig. 1B. It is however obvious that they may quite as well be fastened to the vertical conductors without the scope of the invention being departed from. In Fig. 4 an embodiment is shown, in which the contact springs 6 protrude from the conductors, which together with a selecting bar 11 and its electromagnet form a detachable unit. The conductors 8 are thin bands of metal, from which the contact springs 6 have been cut and bent. Said bands of metal are separated by means of insulating layers and fastened on a supporting bar 14 of insulating material. A lever 22 and an indicating device 7 are fastened on the supporting bar 14 at each crossing point. The lever 22 supports the lifting bar 12, against which the contact springs 6 are resting. The contact springs 6 are bent so, that they stretch downwards.

The horizontal conductors 3 are bands of metal stretched in the strip 17, one for each crossing point. Each strip has a groove 17a, in which the tip of a lever 22 is guided so, that the contact distances between the conductors 3 and the contact springs 6 are fixed.

As well the lever 22 as the conductors 3 allow a spring sufficient for fixing. Since in this case the indicating device 7 is fastened on the supporting bar 14, the lever 22 should be rigid and the spring should take place in the band 3 so, that the indicating device 7 can be adjusted before the vertical unit, which also comprises the selecting bar 11 and its magnet 15 being fastened in the frame 1.

Figs. 5-10 show two other embodiments for the vertical supporting bars 14 with contact springs 6 and conductors 8. In Fig. 5 the conductors 8 are divided into several sets 6a, each of which pertains to a contact spring 6 as shown in Fig. 7. The contact springs 6 are located in the supporting bar 14 and the connections 6a are bent downwards or upwards at one of their flanges and soldered to a corresponding contact spring pertaining to the following crossing point on the other flange. In order to obtain this, the supporting bar 14 is provided with a U-shaped section and with a transversal groove in the two flanges for contact springs. In the space between the flanges there is enough place to locate several connections 6a running in parallel,

the contact springs 6 being considerably narrower at the middle of the supporting bar 14 than at the flanges.

At each crossing point there is a lever 22 above the contact springs 6. Below the contact springs there is at each crossing point an indicating device 7 consisting of partly helical, resilient metal wire. The contact springs 6 hitch in grooves in the lifting bar 12 and stretch downwards. The lifting bar 12 rests against the lever 22. Each contact spring 6 is provided with a soldering ear 20 and therefore the number of contact spring sets connected together thereby can vary.

Figs. 8-9 show another embodiment, in which a U- shaped supporting bar is also used. The vertical conductors 8 are in one piece and soldered to the contact spring 6 at the window 14a in the middle of the supporting bar. At each crossing point there is a lifting spring 23 stretching upwards toward the lifting bar 12 with feeble pressure.

A special bracket 19 for fastening the selecting bar 11 in Fig. 4 is shown as well in Fig. 8 as in Fig. 5, but is not shown in Fig. 6 and Fig. 9.

Fig. shows recesses in the frame 1 for guiding and fastening the supporting bars 14 in Fig. 5 and Fig. 8.

We claim:

1. In a cross-bar switch for automatic telephone systems, a frame, at least one vertical detachable unit arranged on one side of said frame, at least one horizontal detachable unit arranged on the opposite side of said frame, said vertical unit comprising a set of fixed vertical conductors, a selecting bar and a selecting magnet operating said bar, said horizontal unit comprising a set of fixed horizontal conductors, an operating bar and an operating magnet operating said operating bar, contact springs protruding from the conductors in said vertical units at a crossing point between a vertical and a horizontal unit, an indicating device in said vertical unit, a driver fixed to said contact springs, said indicating device being deflected by said selecting bar of the crossing point when said selecting magnet is energized and clutching said driver to the operating bar of the crossing point said driver actuating said contact springs when said operating bar is operated by said operating magnet, and said contact springs bringing each conductor in the vertical unit in contact with a conductor in the horizontal unit at the crossing point.

2. In a cross-bar switch, a frame, a first set of fixed parallel conductors mounted at one side of said frame, a second set of fixed parallel conductors mounted at the opposite side of said frame, said first and said second sets of conductors crossing each other, a selecting bar adjacent and parallel to said first set, an operating bar adjacent and parallel to said second set, a selecting magnet for operating said selecting bar, an operating magnet for operating said operating bar, contact springs protruding from one set of conductors at a crossing point, an indicating device, a driver, said indicating device being deflected by the selecting bar of the crossing point and clutching said driver to the operating bar of the crossing point, said driver actuating said contact springs when the selecting bar and thereafter the operating bar of the crossing point are operated, said contact springs bringing each, conductor in one set at the crossing point in contact with one of the conductors in the other set, and each set of conductors on at least one side of the frame and its associated bar and magnet constituting a separate detachable unit.

3. In a cross-bar switch for automatic telephone systems, a frame, vertical detachable units arranged on one side of said frame, horizontal detachable units arranged on the opposite side of said frame, each of said vertical units comprising a set of fixed vertical conductors, a selecting bar and a selecting magnet operating said bar, each of said horizontal units comprising a set of fixed horizontal conductors, an operating bar and an operating magnet operating said operating bar, at each crossing point between a vertical and a horizontal unit contact springs protruding from the conductors in one of said units, an indicating device, and a driver operating said contact springs, said indicating device being deflected by said selecting bar of the crossing point when said selecting magnet is energized and clutching said driver to the operating bar of the crossing point, said driver when clutched to the operating bar actuating the contact springs of the crossing point, when said operating bar is operated by said operating magnet, and said contact springs bringing each conductor in the vertical unit in contact with a conductor in the horizontal unit at the crossing point.

4. In a cross-bar switch according to claim 2 including means holding the contact springs protruding from one set of conductors in a position fixed in relation to the position of the conductors in the crossing set of conductors at the crossing point.

5. In a cross-bar switch according to claim 2, wherein said second set of conductors and said operating bars are arranged in the same plane and said selecting bars are positioned between said first and second set of conductors.

6. In a cross-bar switch according to claim 3, wherein said horizontal conductors and said operating bars are arranged in the same vertical plane and said selecting bars are positioned between the vertical conductors and said plane.

7. In a cross-bar switch according to claim 2, including a lever protruding from each detachable unit on one side of the frame at each crossing point, said driver in the inoperative position resting against said lever and a free end of said contact springs resting against said driver, and said lever fixing the position of said contact springs in relation to the position of the conductors crossing the unit at the crossing point.

8. The switch according to claim 3, wherein said vertical detachable units comprise the said contact springs, indicating device and driver at the crossing points and a lever adapted to fix the position of the said conductors in the horizontal units in relation to the position of the contact springs at the crossing points.

References Cited in the file of this patent UNITED STATES PATENTS 2,226,666 Lienzen Dec. 31, 1940 2,341,029 Field Feb. 8, 1944 FOREIGN PATENTS 521,004 Great Britain May 9, 1940 

